https://www.hackerrank.com/challenges/2d-array/problem ; Given a 2D Array, find the maximum hourglass sum of all 16 hourglasses

hourglass.cs

using System.IO;
using System;

class Solution {

    // Complete the hourglassSum function below.
    static int hourglassSum(int[][] arr) {
        int[] sum = new int[16];
        int k = 0;
        for (int i = 0; i <= 3; i++)
        {
            for (int j = 0; j <= 3; j++)
            {
                int ia = i + 1; //[ia, ja] is the middle of hourglass
                int ja = j + 1;
                sum[k] = arr[ia][ja] + arr[ia - 1][ja] + arr[ia-1][ja-1] + arr[ia-1][ja + 1] + arr[ia + 1][ja] + arr[ia + 1][ja - 1] + arr[ia + 1][ja + 1];
                k++;
            }
        }

        Array.Sort(sum);
        return sum[15];

    }

    static void Main(string[] args) {
        TextWriter textWriter = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);

        int[][] arr = new int[6][];

        for (int i = 0; i < 6; i++) {
            arr[i] = Array.ConvertAll(Console.ReadLine().Split(' '), arrTemp => Convert.ToInt32(arrTemp));
        }

        int result = hourglassSum(arr);

        textWriter.WriteLine(result);

        textWriter.Flush();
        textWriter.Close();
    }
}